Pretreatment of Corn Stover by Soaking in Aqueous Ammonia

Abstract

Soaking in aqueous ammonia (SAA) was investigated as a pretreatment method for corn stover. In this method, the feedstock was soaked in aqueous ammonia over an extended period (10-60 d) at room temperature. It was done without agitation at atmospheric pressure. SAA treatment removed 55-74% of the lignin, but retained nearly 100% of the glucan and 85% of the xylan. The xylan remaining in the corn stover after SAA treatment was hydrolyzed along with the glucan by xylanase present in the Spezyme CP enzyme. In the simultaneous saccharification and fermentation (SSF) test of SAA-treated corn stover, using S. cerevisiae (DsA), an ethanol yield of 73% of theoretical maximum was obtained on the basis of the glucan content in the treated corn stover. The accumulation of xylose in the SSF appears to inhibit the cellulase activity on glucan hydrolysis, which limits the yield of ethanol. In the simultaneous saccharification and co-fermentation (SSCF) test, using recombinant E. coli (KOll), both the glucan and xylose were effectively utilized, resulting in on overall ethanol yield of 77% based on the glucan and xylan content of the substrate. When the SSCF process is used, the fact that the xylan fraction is retained during pretreatment is a desirable feature since the overall bioconversion can be carried out in a single step without separate recovery of xylose from the pretreatment liquid.

Pretreatment of rapeseed straw by soaking in aqueous ammonia

“…Relatively few studies have reported on application of SAA with lignocellulosic resources, such as corn stover, rice straw, and barley hull [18][19][20]. According to Kim and Lee [17], SAA treatment of corn stover at room temperature and a long treatment period (10-60 days) resulted in removal of 55-74% of the lignin; however, nearly 100% of the glucan and 85% of the xylan were retained. Kim and Lee [18] reported that optimum treatment conditions for SAA of corn stover at moderate temperature were 15% of NH 3 , 60°C, 1:6 of solid-to-liquid ratio, and 12 h treatment time.…”

“…In particular, pretreatment of lignocellulosic resources by soaking in aqueous ammonia has been performed by some research groups using corn stover [15][16][17][18], barley hull [19], and rice straw [20]. Most research on SAA has focused on pretreatment of corn stover [15][16][17][18]. Pretreatment with SAA under moderate conditions (10-15% NH 3 , 65-90°C, 12-24 h) is very efficient as a pretreatment tool for corn stover.…”

Microbial inhibitors: formation and effects on acetone-butanol-ethanol fermentation of lignocellulosic biomass

“…Specifically, steam explosion and hydrothermal pretreatments utilize a temperature range of 121-260°C for 5-60 min (Bondesson et al 2013;Feng et al 2014;Kim et al 2003;Liu et al 2013a, b;Lloyd and Wyman 2005;Mosier et al 2005;Shen and Wyman 2011;Varga et al 2004). Ammonia fiber explosion is conducted at room temperature to 90°C for a retention duration of 11 min to 60 days, using ammonia concentrations of 15 to 25 % (w/w) (Feng et al 2014;Kim et al 2003;Kim and Lee 2005a;Mosier et al 2005;Teymouri et al 2005;. Interestingly, aqueous ammonia can destroy the lignin barrier even at room temperature but it requires a longer duration.…”

Bioconversion of corn stover derived pentose and hexose to ethanol using cascade simultaneous saccharification and fermentation (CSSF)

“…# A669C) and a solid-to-liquid ratio (w/w) of 1:11. The pretreatment was performed in screw-capped Pyrex media bottles (250 ml) at 60°C (maintained by convection oven) without agitation for 12 h. These conditions were chosen based on the results obtained previously for SAA pretreatment of corn stover [15,16]. The pretreated corn stover was washed with deionized (DI) water using vacuum filter and fluted filter paper (Fisher Cat.…”